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<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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<body>
    
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<script>
    //普通函数
    let arr = [1,2,3,4];
    let newarr = arr.filter(function (item){
        return item < 2.5
    })
    console.log(newarr); //[1.2]

    //箭头函数
    let newarr1 = arr.filter(item=>item<2.5);
    console.log(newarr1); //[1.2]
</script>